ML110030842

E-mail from J. Tsao, NRC to E. Michel, NRC, Et Al; Re Oconee Ssf Asw Leak

ML110030842
Person / Time
Site:	Oconee
Issue date:	08/31/2009
From:	John Tsao Office of Nuclear Reactor Regulation
To:	Mel Holmberg, Eric Michel Office of Nuclear Reactor Regulation, NRC/RGN-II
References
FOIA/PA-2011-0021
Download: ML110030842 (3)

Text

Stamm, Eric From: Tsao, John ký- \' -

Sent: Monday, August 31, 2009 12:51 PM To: Michel, Eric; Holmberg, Mel Cc: Riggs, Eric; Chan, Terence; Franke, Mark; Sabisch, Andrew

Subject:

RE: OCO SSF ASW leak

Eric, I think that for a pin hole that is caused by wall thinning, it does not matter whether the flaw initiation site was from the ID or OD surface in terms of calculating allowable thickness (Tallow) and predicted thickness for the next ISI (Tp) in GL 90-05. GL 90-05 references ASME Code Case N-480 which provides Tallow & Tp calculation methodology.

I think that there probably would be some slight differences in Tallow & Tp for a flaw that initiates at OD vs a flaw that initiates at the ID surface, depending the localized stress state at the pinhole (in tension or compression).

However, the Tallow and Tp calculations in Code case N-480 are based on the global pipe loads (such as bending loads) and axial and hoop stresses. In this case, Tallow and Tp probably would not be affected by whether the flaw is initiated from OD or ID.

GL 90-05 was issued at the time (circa 1990) when most of pipe leaks were caused by erosion/corrosion/flow-accelerated corrosion from the ID surface, not from the OD surface. Therefore OD degradation was not addressed in GL 90-05.

Thanks.

John From: Michel, Eric Sent: Monday, August 31, 2009 11:31 AM To: Holmberg, Mel; Tsao, John Cc: Riggs, Eric; Chan, Terence; Franke, Mark; Sabisch, Andrew

Subject:

RE: OCO SSF ASW leak Thanks Mel, When the issue came up I went back to the email you'd sent me regarding your finding at Monticello. I agree this is potential issue here at OCO too.

They used a procedure based on SE-797 to do thickness measurements for their flaw evaluation. Could be an issue because it's not a qualified procedure - see Section XI, App I, Table 1-2000-1, Supplement 12.

Additionally, they didn't use an SE-213 based procedure to do any augmented exams (especially in the vicinity of the original flaw). If there were non-through-wall defects near the TW flaw they wouldn't detect them with the SE-797 procedure, and therefore may exclude potential defects that are required to be combined with the TW defect from the GL 90-05 analysis.

I've also got a concern with the use of GL 90-05 Enclosure 1. Limitations of the Enclosure state that the "flaw... originates from the inner diameter of the pipe..." I haven't seen any justification to use GL 90-05 for a flaw initiating from the OD (the source of corrosion is considered to be a very narrow pit of general corrosion caused by a failure of the coal tar coating on the outside of the pipe).

Th~nksý for keeping usin mind! Any thoughts on the above would be appreciated.

Eric From: Holmberg, Mel Sent: Monday, August 31, 2009 11:17 AM To: Tsao, John; Michel, Eric Cc: Riggs, Eric; Chan, Terence

Subject:

RE: OCO SSF ASW leak I do not know any of the specific details for this issue. I would presume that the licensee's quality assurance requirements mimic our Appendix B criterion IX requirement that NDE is a special process that is required to be performed by staff, procedures and equipment qualified to applicable Codes and Standards. For piping products, you may start with the construction Code say Section III or perhaps B31.1. These construction Codes typically send you to Section V, Article 5 related to UT of materials. This then would send you to an SE type standard for thickness measurements. From the 2001 Code this is ASTM E-797-95 (attached). Also note that thickness measurements are not considered effective for pitting type defects (see table A-1 10 on Page 18 from Section V general requirements in second document).

Mel From: Tsao, John Sent: Friday, August 28, 2009 12:28 PM To: Michel, Eric Cc: Riggs, Eric; Chan, Terence; Holmberg, Mel

Subject:

RE: OCO SSF ASW leak

Eric, The end of next week is okay.

I think that the licensee performed wall thinning inspection to satisfy the ASME Code Section III requirements regarding wall thickness (i.e., to satisfy the design basis regarding the pipe wall thickness).

I do not know much about the specific UT requirements for the Section 111 wall thickness requirement.

The licensee needs to perform a wall thickness calculations in the PDO to show that the existing and degraded wall thickness satisfy Section III requirements. so far I have not seen in the PDO that a wall thinning calc was done.

Licensees (e.g., Byron) have used Appendix F of the ASME Code Section III to calculate an allowable wall thickness to demonstrate that a reduced wall thickness will still satisfy the Section III requirement.

Byron also inspected many regions of the service water pipes using UT to show that the wall thickness satisfy the allowable. Call Mel Holmberg. He has lots info on the Byron service water leak event in 2008.

I do not know if wall thinning inspection by UT is part of the Section XI UT requirement. I could be wrong but I do not think Section XI, IWB-3000 provides acceptance criteria for dispositioning wall thinning. IWB-3000 is for planar flaws or laminar flaws.

Thanks.

John From: Michel, Eric Sent: Friday, August 28, 2009 10:55 AM 2

To: Tsao, John Cc: Riggs, Eric

Subject:

RE: OCO SSF ASW leak

John, Will the end of next week work?

One thing I noticed in the operability determination was that they're saying the UT method wasn't qualified, so they didn't meet Section XI requirements. I imagine this is something they'd at least need relief for if we're going to accept the idea that is was a "best effort examination."

Eric From: Tsao, John Sent: Friday, August 28, 2009 9:36 AM To: Michel, Eric; Chan, Terence Cc: Franke, Mark; Riggs, Eric

Subject:

RE: OCC SSF ASW leak

Eric, Terence may assign the review of the prompt determination of operability to someone else in my branch, but I will be reviewing it also.

when do you want our feedback? please give us a date and time.

Thanks.

John From: Michel, Eric Sent: Friday, August 28, 2009 9:28 AM To: Chan, Terence Cc: Tsao, John; Franke, Mark; Riggs, Eric

Subject:

OCO SSF ASW leak

Terence, We received the OCO operability determination for their SSF ASW piping leak yesterday. We'd appreciate someone taking a look at the sections associated with the ASME Code compliance (GL 90-05), and the water hammer evaluation. The overall PDO starts on page 3, the water hammer analysis starts on page 5, and the Code compliance section starts on page 10. Of course, if you find any other areas of concern we'd appreciate your thoughts. Thanks.

Eric 3